Abstract: Taking the Yangling of Shaanxi as a case and selecting field plot scale as the assessment unit, the farmland soil fertility quality was evaluated by using integrated fertility index. According to the statistical analysis for sample number rationality, the regional soil fertility assessment based on 27 sampling sites were sufficient to meet the required accuracy of 15% and 20% relative error under 90% confidence level. The minimum data set components including soil organic matter, total nitrogen, total phosphorus, total potassium, available phosphorus, available potassium, CEC, and calcium carbonate were selected through calculating the Norm values based on principal components analysis, and the non-linear membership function was used to transform the indicators into dimensionless data and to evaluate single indicator. The radar plot was used to reflect the single factor fertility and the integral fertility. It was shown that total phosphorus and calcium carbonate were the limiting factors for the soil fertility quality in the study area, and the integrated fertility index at field plot scale
was 0.7-0.8.

Key words: Zea mays, Allelochemical, Cyclic hydroxamic acids, Exudation